Coarse-grained material properties of the cellular micro-environment, such as its stiffness and viscosity, are known to play crucial roles in determining cell structure and function [1]}, [2]}, [3]}.  [fig:MasterPlot2]Figs. 1 a, b are taken from two different cell culture experiments on substrates of varying stiffness. In the first experiment ([fig:MasterPlot2]Fig. 1 a), it was shown that, under certain conditions, bovine endothelial cells formed networks preferentially on stiffer substrates (\(E \sim 10\)  KPa) [4]}, More recently( [fig:MasterPlot2]Fig. 1 b), it was shown that human endothelial cells assemble into networks on softer substrates (\(E \sim 1\)  kPa) but fail to do so on stiffer substrates, independently of the type of hydrogel used [5]}. Both these experiments show that EC network formation is sensitive to substrate stiffness, and therefore suggest that cell mechanical interactions mediated by the substrate are involved.
